The advent and usefulness of modular architectures for semiconductor fabrication fluids are disclosed in U.S. Pat. No. 5,836,355 issued to Markulec et. al. on Nov. 17, 1998, in U.S. Pat. No. 5,964,481 issued to Buch on Oct. 12, 1999, and in U.S. Pat. No. 6,085,783 issued to Hollingshead on Jul. 11, 2000. These various architectures, or modular building blocks, for fluid delivery afford ease of fluid system design, ease of assembly, reduced size, improved serviceability, and reduced wetted surface area when compared to conventional tubulated-and-welded fluid delivery systems.
The modular blocks, sometimes referred to as substrates, disclosed in the patents cited above, share some common features, among which are the planar block interfaces which, when compressed one against another with an interdisposed seal, form a contiguous and hermetic path for fluid delivery. Compression of multiple blocks may be effected several ways. One way is to use “long” bolts cut to the length specific to a particular multi-block assembly and which, when inserted through accommodating holes in the plurality of blocks and fasteners thereon tightened, compress all the blocks, block interfaces, and inter-block seals simultaneously. Another way is to bolt, in turn, one block or substrate to another in a sequential and iterative fashion with “short” bolts to accomplish the desired multi-block assembly.
When assembled into fluid delivery panels and completed by the attachment of functional control elements such as valves, regulators, pressure transducers and the like, these modular fluid delivery systems are currently used in virtually all types of semiconductor fabrication processes. By their very nature, these processes often employ fluids that are extremely toxic and/or volatile. Further, introduction of contamination, such as air, to various of these fluids, or escape of these fluids to air, may result in failure of the process and loss of product, downtime of the process, or worse, severe injury or fatality to operating personnel. Specifically, it is imperative that the hermeticity, or seal integrity, of the compressed-and-sealed interfaces of all the blocks comprising the fluidic delivery system remain uncompromised throughout delivery, installation, and operational lifetime of the system, making the mechanical and leak integrity of bolted-together modular fluid-delivery systems is of the highest priority.
Current practice for sealing modular fluid-delivery blocks one to another, wherein seals are required, calls for the use of compressible toroidal metal gaskets often referred to as C-seals. This type of seal has been specified by Semiconductor Equipment and Materials International (SEMI) draft document 2787.1 as the standard seal for use in sealing components, such as valves, regulators, filters, etc. to modular fluid-delivery blocks in the semiconductor industry, and as such has become the de facto standard for inter-block seals as well. Examples of these seals may be seen in U.S. Pat. No. 4,603,892 issued to Abbes on Aug. 5, 1986 and U.S. Pat. No. 4,218,067 issued to Halling on Aug. 19, 1980. In general, these seals have been designed to be compressed between opposing metal surfaces to form a hermetic seal between them. The seals themselves are designed to have inherent elastic deformation sufficient to maintain conformation to said opposing metal surfaces, when compressed to prescribed limits between opposing and appropriately-finished metal surfaces, with sufficient resilient force to create a hermetic seal.
The primary force that resists shear between any two compressed and C-sealed modular fluid-delivery blocks is simply the arithmetic product of the compressive force and the coefficient of friction of the inter-block surfaces. Because the C-seal itself is designed to be a compliant and compressible sealing element between the blocks, its frictional coefficient-compression product provides negligible shear resistance to the overall assembly. Because of size and weight constraints in modern semiconductor fabrication equipment and facilities, the semiconductor industry has placed considerable emphasis upon size-reduction of modular fluid-delivery systems. A significant requirement of such size reduction is the necessity to use smaller bolts for the assembly, and therefore the seal compression, of smaller modular blocks. As a consequence of smaller bolts, available compressive forces are reduced because of reduced bolt torque capability, with a corresponding reduction of force to resist block-to-block shear stress during shipment, installation, and operation of the modular fluid delivery systems.
All fluid delivery systems, including modular block architectures, for semiconductor processing applications must pass rigorous shock and vibration qualification, as put forth in SEMI document #3091, as well as meet practical objectives for robustness as presented earlier. What is needed, then, is a practical, cost-effective method to provide mechanical robustness, particularly shear resistance, between modular blocks of increasingly small sizes compressed with increasingly smaller bolts.